Hey, long story short, when coming up with a world setting for a tabletop game, I decided bitcoin would be used as the currency. However, there are several odd situations that arose in the world, that I don't know how bitcoin would react to.

The first situation, is one city, with approximately 10% of the world's population, and oh say..... 20% of the world's bitcoins was suddenly walled off from the rest of the world. Both sides believed the other to be permanently gone, and have adjusted policies as such. Ten years after this fizzure, they are re-united. What would happen to the bitcoins when the two drastically different chains are merged?

The second situation, one entity in this setting is supernaturally lucky. aside from mining success, what else could happen to him? Would it be theoretically possible to accidentally produce some Richdude's bitcoin address and take Richdude's coins?

Hey, long story short, when coming up with a world setting for a tabletop game, I decided bitcoin would be used as the currency. However, there are several odd situations that arose in the world, that I don't know how bitcoin would react to.

The first situation, is one city, with approximately 10% of the world's population, and oh say..... 20% of the world's bitcoins was suddenly walled off from the rest of the world. Both sides believed the other to be permanently gone, and have adjusted policies as such. Ten years after this fizzure, they are re-united. What would happen to the bitcoins when the two drastically different chains are merged?

The shorted chain would be consumed by the longer one, invalidating all generated coins and any transaction involving those coins. However, only one connection would be needed between both sides to prevent this.

The second situation, one entity in this setting is supernaturally lucky. aside from mining success, what else could happen to him? Would it be theoretically possible to accidentally produce some Richdude's bitcoin address and take Richdude's coins?

Yes, but the sun will expand and consume the Earth before that would happen, statistically.

What, if Dr. Evil started in the early days of Bitcoin a fork, i.e. its own isolated network of super computers generating bitcoin after bitcoin. And this network is so strong that it will have the "longer chain"*. And one day, Dr. Evil decides to reunite both the normal and the evil network. Et voila, many bitcoins will be eaten by Dr. Evil's network.